The present disclosure relates to a switching circuit and an RF (Radio Frequency) switch including the same.
Along with developments in wireless communications technologies, various communications standards have been simultaneously implemented. In addition, along with a trend for miniaturized wireless communications modules and high performance portable terminals, there has been a need for compliance with a plurality of communication standards in a single portable terminal. Thus, more frequency bands need to be supported by a single portable terminal.
That is, existing second-generation (2G) and third-generation (3G) communications technologies have been supplemented with new communications technologies, such that portable communications terminals compliant with fourth-generation (4G) communications schemes such as Long Term Evolution (LTE) have been developed. In addition, in the area of Wi-Fi communications, portable communications terminals have been implemented with the ability to operate with the IEEE 802.11ac standard in addition to the existing IEEE 802.11b/g/n to enhance marketability thereof.
In accordance with this trend, there has also been demand for support for various frequency bands within a radio frequency (RF) front end field. For example, support for various frequency bands with respect to an RF switch positioned on a signal path between an antenna and an RF chipset has been demand. Therefore, a Single Pole Double Throw (SPDT) type switch has been used in various applications.
Recently, as processing technologies based on field effect transistors (FETs) such as complementary metal-oxide semiconductors (CMOS) or the like have been developed, FETs have been widely used to manufacture electrical switches. However, when a high power RF signal is applied to such an electrical switch, a source voltage swing may be lower than a threshold voltage (Vth), and in this case, problems may arise in that the switch may be unintentionally turned on. That is, when a gate of an FET is turned off to zero (0) V, if negative swing of an input signal applied to a source is equal to or higher than the threshold voltage Vth to satisfy the condition Vgs>Vth, problems arise in that the switch may be turned on.
The Related Art Document discloses a radio frequency (RF) shield switch, in which a source and bulk simultaneously short-circuit when an RF switch is turned on, thereby reducing a threshold voltage of a main transistor. However, the Related Art Document does not disclose that a voltage level of Vgs is maintained to a threshold voltage level or less using an inverter so as to prevent a switch from being turned on even when a large RF signal is suddenly input.